Spectrophotometric determination of hydrazine

Hydrazine is determined spectrophotometrically by forming the derivative 2,4-dinitrophenylhydrazine from 2,4-dinitrochlorobenzene. The formed dinitro derivative undergoes condensation reaction to form the hydrazone with p-dimethylaminobenzaldehyde (p-DAB). The resulting yellow colored product is stable in acidic medium and has a maximum absorption at 458 nm. The colour system obeys Beer's law in the range 0–7 μg of hydrazine in an overall volume of 25 mL. The molar absorptivity is calculated to be 8.1 × 104 L mol−1 cm−1 with a correlation coefficient of 0.998. The relative standard deviation is 1.7% (n = 10) at 6 μg of hydrazine. Interferences due to foreign ions have been studied and the method has been applied for the determination of hydrazine in boiler feed water.